WO2009143351A2 - Séparation de nanoparticules utilisant une diffusion raman anti-stokes cohérente - Google Patents

Séparation de nanoparticules utilisant une diffusion raman anti-stokes cohérente Download PDF

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WO2009143351A2
WO2009143351A2 PCT/US2009/044848 US2009044848W WO2009143351A2 WO 2009143351 A2 WO2009143351 A2 WO 2009143351A2 US 2009044848 W US2009044848 W US 2009044848W WO 2009143351 A2 WO2009143351 A2 WO 2009143351A2
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nanoparticles
raman
stokes
photoresist
nanotubes
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PCT/US2009/044848
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English (en)
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WO2009143351A3 (fr
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Eric Mazur
Eric Diebold
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President & Fellows Of Harvard College
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Priority to US12/989,833 priority Critical patent/US8439201B2/en
Publication of WO2009143351A2 publication Critical patent/WO2009143351A2/fr
Publication of WO2009143351A3 publication Critical patent/WO2009143351A3/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82B—NANOSTRUCTURES FORMED BY MANIPULATION OF INDIVIDUAL ATOMS, MOLECULES, OR LIMITED COLLECTIONS OF ATOMS OR MOLECULES AS DISCRETE UNITS; MANUFACTURE OR TREATMENT THEREOF
    • B82B3/00—Manufacture or treatment of nanostructures by manipulation of individual atoms or molecules, or limited collections of atoms or molecules as discrete units
    • B82B3/0061—Methods for manipulating nanostructures
    • B82B3/0071—Sorting nanostructures

Definitions

  • the present invention relates generally to methods and systems of screening particles, and particularly, such methods that employ Raman scattering for separating particles of different types.
  • Raman spectroscopy is a powerful technique that allows identifying molecules via their characteristic spectral fingerprints. It relies on inelastic scattering of incident photons by a molecule, via coupling to its vibrational modes, to provide an essentially unique signature for that molecule.
  • inelastic scattering commonly known as Raman scattering
  • Raman scattering can cause a decrease or an increase in the scattered photon energy, which appear as "Stokes” and "anti-Stokes" peaks in a wavelength-dispersed spectrum of the scattered photons.
  • a drawback of Raman spectroscopy is that the probability for occurrence of such scattering is small (typically presented as the scattering cross-section).
  • Raman scattering cross sections can, however, be significantly enhanced by placing the molecules on or near roughened nanoscale metal surfaces.
  • Such a mode of performing Raman spectroscopy is commonly known as surface enhanced Raman spectroscopy (SERS).
  • SERS surface enhanced Raman spectroscopy
  • Raman-active molecules can be placed on both aggregates of, and single metallic nanoparticles.
  • different metallic nanoparticles can provide widely varying enhancement factors. In other words, not all metallic nanoparticles are equally SERS-active. Accordingly, there is a need for methods and systems for screening metallic nanoparticles for their SERS activity, and there is a need for such methods that can efficiently separate SERS-active nanoparticles from SERS-inactive nanoparticles.
  • the present invention provides a method for separating particles that exhibit different Raman characteristics. Such differing Raman characteristics can be based on different vibrational energy levels of various constituents of the particles and/or based on Raman-scattering enhancement factors that one or more constituents of the particles provide.
  • particles exhibiting at least two types of Raman scattering characteristics are contacted with a photopolymerizable medium (e.g., a resin), e.g., by introducing (e.g., dispersing) the particles into a photopolymerizable medium.
  • the particles are then illuminated with radiation so that the Raman-active constituent of the nanoparticles would mediate the generation of Raman blue-shifted anti-Stokes radiation.
  • the efficiency of the generation of such blue-shifted anti-Stokes radiation can differ for different particle types.
  • the particles comprise metallic nanoparticles on which Raman- active molecules are adsorbed
  • the extent to which the nanoparticles enhance Raman scattering cross sections of the adsorbed molecules can determine how efficiently the blue-shifted anti-Stokes radiation is generated.
  • the incident radiation can be selected to be on resonance with a vibrational transition of one type of the particles and not with the other type(s).
  • the on-resonance particles would generate Raman scattered blue shifted anti-Stokes radiation more efficiently than the off-resonance particles.
  • the resin is selected such that it will polymerize in response to the blue shifted anti-Stokes radiation (the resin is preferably selected not to undergo polymerization in response to the incident radiation).
  • the particles exhibiting a greater Raman scattering cross-section mediate the generation of the blue shifted radiation more efficiently, a portion of the resin surrounding them undergoes a greater degree of polymerization than the resin surrounding those particles exhibiting significantly lower Raman scattering cross- sections.
  • the resin surrounding the particles that do not exhibit high Raman-scattering cross-sections remains substantially (or entirely) unpolymerized.
  • Such a non-uniform polymerization of the resin can in turn give rise to non-uniform addition of polymeric mass to particles of different types.
  • This non-uniformity can then be utilized to separate the particles exhibiting high Raman-scattering cross-section from others based on their mass difference (e.g., via centrifugation), or differences in their mobility or size, or other suitable characteristics based on the added polymeric mass.
  • the particles to which the polymeric resin has been added can exhibit a different mobility, e.g., a different mobility in a fluid and/or under the influence of an electric field, than others.
  • the present invention provides methods for screening nanoparticles, and particularly metallic nanoparticles, based on the level of Raman scattering enhancement that they provide.
  • the methods of the invention can be employed to separate SERS-active nanoparticles (herein referred to also as "hot" nanoparticles or particles), from SERS-inactive or less active nanoparticles.
  • a SERS-active nanoparticle can sufficiently enhance the Raman scattering cross-section associated with a Raman-active molecule in its vicinity (e.g., a molecule adsorbed on it surface) so as to render single-molecule Raman detection feasible.
  • the screening process employs SECARS (surface enhanced coherent anti-Stokes Raman scattering) anti-Stokes photons generated via dye molecules adsorbed onto nanoparticles (a dye molecule can act as a mediator for the generation of anti-Stokes photons in the 4-wave mixing SECARS process) to selectively polymerize a resin around the nanoparticles that enhance the SECARS process.
  • SECARS surface enhanced coherent anti-Stokes Raman scattering
  • the polymerized resin adds mass to the "hot” nanoparticles, which in turn allows their separation, e.g., via centrifugation or other techniques.
  • the polymerized resin can then be removed from separated “hot” particles and those particles can be suspended in a liquid. In this manner, the population percentage of the "hot” particles in a solution can be enriched.
  • a method of separating carbon nanotubes of different types includes dispersing a plurality of carbon nanotubes with at least two different types in a photopolymerizable medium, where the two nanotube types are characterized by their varying Raman scattering characteristics (or their different electrical conductivity).
  • the dispersed nanotubes can then be illuminated with incident radiation so as to cause resonant Raman scattering from nanotubes of one type and thereby generate blue-shifted anti-Stokes radiation having a wavelength suitable for polymerizing the medium.
  • the incident radiation is, however, selected to be off- resonance for the nanotubes of the other type.
  • the blue-shifted anti-Stokes radiation causes polymerization of at least a portion of the resin surrounding the on-resonance nanotubes adding polymeric mass to those nanotubes, while the resin surrounding the off-resonance nanotubes remains substantially (or entirely) unpolymerized.
  • the invention provides methods of electrically isolating, e.g., via formation of an electrically non-conducting coating, one or more nanoparticles, e.g., carbon nanotubes, disposed over a substrate, e.g., a silicon substrate.
  • the method can include forming, e.g., via spin-casting, a negative-tone photopolymerizable photoresist layer over the nanoparticles, e.g., a layer having a thickness in a range of about 0.1 to about 5 microns such that the nanoparticles are contained within the layer.
  • Incident radiation can then be directed to the photoresist covering the nanoparticles, e.g., to expose the nanoparticles and/or one or more Raman- active molecular species close to the nanoparticles (e.g., in the optical near field of the nanoparticles) to the radiation, so as to cause generation of blue-shifted anti-Stokes photons (e.g., via CARS or SECARS processes) such that the anti-Stokes photons are absorbed by at least portions of the photoresist surrounding the nanoparticles to cause their polymerization, thereby forming an electrically insulating coating that at least partially surrounds the nanoparticles.
  • the incident radiation can include, e.g., two pump beams each at a pump frequency ( ⁇ p ) and a Stokes beam at a frequency of ( ⁇ s ) such that a difference between the pump and the Stokes frequencies corresponds to a vibrational frequency of at least one Raman active vibrational mode of the nanoparticles.
  • the frequency of the pump beam or the frequency of the Stokes beam, or both can be selected to correspond to at least one electronic transition (transition between two electronic states) of the nanoparticles so as to enhance the resonant coherent anti-Stokes Raman scattering.
  • the difference between the frequency of the pump photons and the frequency of the Stokes photons can correspond to the vibrational frequency of at least one Raman active mode of one or more molecules in the vicinity of the nanoparticles (e.g., in the optical near-field of the nanoparticles).
  • the frequency of the pump photons and/or the frequency of the Stokes photons can correspond to the frequency of at least one electronic states transition (or the frequency of at least one plasmon resonance) of the nanoparticles, that is, either the pump photons and/or the Stokes photons can be in resonance with at least one electronic transition or at least one plasmon mode of the nanoparticles.
  • the nanoparticles then cause an enhancement of the resonant Raman scattering from the molecules in their vicinity to generate anti-Stokes photons for causing polymerization of layers of the photoresist surrounding the nanoparticles.
  • at least one constituent of the photoresist surrounding the nanoparticles having one or more Raman active modes can be utilized to generate anti-Stokes photons.
  • the nanoparticles can enhance the effective Raman scattering cross-section of the portions of the Raman-active constituent in their proximity(e.g., within the optical near field, for example, within a distance of less than about 100 nm) to generate sufficient number of anti-Stokes photons for polymerizing portions of the photoresist surrounding the nanoparticles.
  • the other portions of the constituent can exhibit much lower Raman-scattering cross-section.
  • one or more molecular species that exhibit at least one Raman- active mode can be deposited on the surface of the nanoparticles prior to the deposition of the photoresist layer such that those molecular species would mediate the generation of the blue-shifted anti-Stokes photons.
  • the nanoparticles can be coated initially, at least partially, with a molecular layer exhibiting one or more Raman active modes and subsequently a photoresist layer can be formed over the coated particles to contain them.
  • the Raman-active molecular layer can then be exposed to incident radiation to generate blue-shifted anti-Stokes photons via coherent resonant Raman scattering.
  • a self-assembled monolayer of an alkanethiol molecule can be deposited over a metallic nanoparticle to form a Raman-active layer that can mediate the generation of blue shifted anti-Stokes photons.
  • the incident radiation can be directed into the photoresist containing the nanoparticles to cause generation of the anti-Stokes photons either via resonant Raman scattering of incident photons from the nanoparticles themselves or via resonant coherent anti-Stokes Raman scattering from molecules in their vicinity (e.g., in the optical near field of the nanoparticles).
  • the incident radiation can be, e.g., in the form a radiation pulses.
  • the radiation pulses can have a duration in a range of about 20 femtoseconds to about
  • the unexposed portions of the photoresist can be removed, e.g., by dissolving those portions in a developing agent, to leave behind the coated nanoparticles on the substrate.
  • photoresist resins and developing agents can be employed in the above method.
  • An example of suitable photoresists includes, without limitation, epoxy- based polymers, such as resists marketed by MicroChem Corp. of Newton, Massachusetts, U.S.A. under trade designations SU-8, and some examples of suitable developing agents include, without limitation, propylene glycol, monomethyl ether acetate (PGMEA) and acetone.
  • PMEA monomethyl ether acetate
  • a method for selectively removing one type of nanoparticles from a collection of nanoparticles of different types that are disposed over a substrate includes forming, e.g., via spin-casting, a photoresist layer over a plurality of nanoparticles of at least two different types disposed on a substrate, e.g., a silicon substrate, such that the nanoparticles are contained at least partially within the resist layer.
  • the nanoparticles are then exposed to incident radiation such that the nanoparticles of one type would mediate the generation of blue-shifted anti-Stokes photons via direct resonant Raman scattering or via enhancing the resonant Raman scattering of nearby molecules (e.g., via CARS or SECARS processes), while the nanoparticles of the other type(s) do not mediate generation of a substantial number of anti-Stokes photons, if any.
  • the photoresist is selected such that at least portions of the resist that are exposed to the anti-Stokes photons absorb those photons to change their solubility in a developing agent.
  • the photoresist comprises a positive-tone photoresist
  • the absorption of the anti-Stokes photons can render the photoresist portions absorbing those photons soluble to a developing agent (or enhance the photoresist's solubility to a developing agent).
  • the photoresist comprises a negative-tone photoresist
  • the photoresist portions that absorb the anti-Stokes photons become polymerized and hence less soluble to a developing agent.
  • a developing agent can be applied to the photoresist layer to remove the soluble portions thereof, thereby uncovering one type of the nanoparticle while leaving the other type(s) covered.
  • the uncovered nanoparticles can then be removed, e.g., via known physical or chemical etching processes, leaving behind the covered nanoparticles of the other type(s).
  • the photoresist covering the nanoparticles that are left behind can then be removed, if desired, by utilizing a variety of known chemical treatments (typically referred to as "resist stripping" processes).
  • resist stripping is accomplished by removing the exposed resist using either a liquid solvent (typically an organic solvent such as acetone, or acidic mixtures, such as Pirhana etch-sulfuric acid and hydrogen peroxide; or using a dry etch, such as an oxygen plasma.
  • ashing is often called "ashing.”
  • the incident radiation can comprise two pump beams each at a pump frequency ( ⁇ p ) and a Stokes beam at a frequency of ( ⁇ s ) such that a difference between the pump and the Stokes frequencies corresponds to a vibrational frequency of at least one Raman active vibrational mode of one type of the nanoparticles but is distinct from the vibrational frequencies of the Raman-active modes of the other type (or types) of the nanoparticles.
  • the pump photons or the Stokes photons can be resonant with at least one electronic transition of the nanoparticles.
  • resonant Raman scattering of the incident radiation from one or more Raman-active molecules close to the nanoparticles can be utilized to selectively generate anti-Stokes photons in the vicinity of one type of the nanoparticles but not the other type(s).
  • the difference between the frequency of the pump photons and that of the Stokes photons can be selected to correspond to the vibrational frequency of at least one Raman active mode of the nearby Raman-active molecules (e.g., a Raman active constituent of the surrounding photoresist).
  • the nearby molecules can be located within the near optical field of the nanoparticles.
  • the frequency of the pump photons or the frequency of the Stokes photons can be selected to be in resonance with at least one plasmon resonance of one type of the nanoparticles but be off-resonance relative to the plasmon resonances of the other type(s). In this manner, the nanoparticles of one type
  • the nanoparticles providing Raman scattering enhancement can be removed from the substrate by utilizing the steps discussed above.
  • resonant nanoparticle refers to a nanoparticle that exhibits at least Raman active mode having a vibrational frequency corresponding to the frequency difference between the pump photons and Stokes photons in a CARS process or exhibits at least one electronic state resonance (or plasmon resonance) at a frequency corresponding to either the Stokes or the pump frequencies.
  • non-resonant nanoparticle refers to a nanoparticle that does not include a Raman active vibrational mode corresponding to the difference between the pump and Stokes frequencies, nor does it include an electronic state resonance (or plasmon resonance) at a frequency corresponding to that of the pump photons or the Stokes photons.
  • the incident radiation can be, e.g., in the form radiation pulses.
  • the radiation pulses can have a duration in a range of about 20 femtoseconds to about 5000 femtoseconds, and an energy in a range of about 1 nanoJoules to about 1 Joules.
  • the above method can be utilized to selectively remove metallic carbon nanotubes from a collection of metallic and semiconducting carbon nanotubes disposed over a substrate, or vice versa.
  • a variety of photoresists and developing agents can be utilized in the above method for selective removal of one type of nanoparticles from a collection of nanoparticles of different types.
  • An example of suitable photoresist include, without limitation, resists marketed by MicroChem Corp. of Newton, Massachusetts, U.S.A. under trade designations SU-8, and some examples of suitable developing agents include, without limitation, propylene glycol monomethyl ether acetate (PGMEA) and acetone.
  • PMEA propylene glycol
  • FIGURE 1 is a flow chart depicting various steps of an exemplary embodiment of a method according to the teachings of the invention for separating nanoparticles exhibiting differing Raman-scattering enhancement
  • FIGURE 2 presents a schematic energy diagram depicting spontaneous Raman scattering and CARS four-wave mixing process
  • FIGURE 3 is an exemplary system for practicing the methods of the invention
  • FIGURE 4 is a flow chart depicting various steps of an exemplary embodiment of a method according to the teachings of the invention for separating metallic carbon nanotubes from semiconducting carbon nanotubes,
  • FIGURE 5 is a flow chart depicting various steps in an embodiment of a method according to the teachings of the invention for electrically insulating one or more nanoparticles disposed over a substrate,
  • FIGURE 6A is a schematic perspective view of a substrate on which a plurality of carbon nanotubes are disposed
  • FIGURE 6B is a schematic side view of the substrate of FIGURE 6A after deposition of a negative-tone photoresist layer over the carbon nanotubes
  • FIGURE 6C schematically shows that portions of the negative photoresist that have been polymerized (shaded areas) via absorption of blue-shifted anti-Stokes photons to form an electrically insulating coating around the carbon nanotubes,
  • FIGURE 7 is a schematic view of certain parts of a device in which carbon nanotubes are incorporated, where the carbon nanotubes are electrically isolated from other parts of the device by employing the teachings of the invention,
  • FIGURE 8 is a schematic view of a field effect transistor in which a carbon nanotube is incorporated, where the carbon nanotube is electrically isolated from other parts of the device by employing the teachings of the invention,
  • FIGURE 9 is a flow chart depicting various steps in an embodiment of a method for selectively removing one type of nanoparticles from a collection of nanoparticles of different types in accordance with the teachings of the invention.
  • FIGURE 1OA schematically depicts a substrate over a surface of which a plurality of carbon nanotubes of different types are disposed and a positive-tone photoresist layer disposed over that surface to cover the nanotubes,
  • FIGURE 1OB schematically shows that a portion of the photoresist (shaded area) has been exposed to anti-Stokes photons generated by a resonant carbon nanotube in its vicinity, thereby rendering that photoresist portion soluble to a developing agent
  • FIGURE 1OC shows the photoresist layer after the removal of the soluble photoresist portion by utilizing a developing agent, thereby uncovering the resonant carbon nanotube
  • FIGURE 1OD shows the photoresist layer after removal of the uncovered carbon nanotube.
  • the present invention is generally directed to methods and systems for separating particles (e.g., nanoparticles) by employing their Raman scattering characteristics including, without limitation, differences in intrinsic vibrational levels of such particles and/or their efficacy in improving surface enhanced Raman scattering (SERS) exhibited by Raman-active molecules adsorbed on such particles or present in their vicinity.
  • SERS surface enhanced Raman scattering
  • the term SERS-active nanoparticles is used to refer to those nanoparticles that enhance Raman scattering of a Raman-active molecule adsorbed thereon by a factor more than a threshold (e.g., by more than about 10 4 or 10 6 ), while the term SERS-inactive nanoparticles is used to refer to those nanoparticles that provide no enhancement or a weak enhancement of the Raman scattering (e.g., an enhancement less than about 10 4 ).
  • nanoparticle is known in the art, and is used herein to refer to a particle (e.g., a collection of atoms, such as gold or silver atoms) whose size in at least one dimension (e.g., in x, y, or z dimension), and in some cases all dimensions, is equal or preferably less than about 1 micron.
  • a particle e.g., a collection of atoms, such as gold or silver atoms
  • size in at least one dimension e.g., in x, y, or z dimension
  • it can refer to particle having an average cross-sectional diameter in a range of about 1 nanometer to about 1 micron, or in a range of about 1 nm to about 300 nm, or in a range of about 5 nm to about 100 nm. It should, however, be understood that the teachings of the invention can be equally applicable to particles having larger sizes.
  • a plurality of nanoparticles are initially (step 1) incubated with a Raman-active dye to cause the dye molecules to be adsorbed onto the nanoparticles (e.g., via Van-der-Waals, ionic or in some cases covalent interactions).
  • a Raman-active dye to cause the dye molecules to be adsorbed onto the nanoparticles (e.g., via Van-der-Waals, ionic or in some cases covalent interactions).
  • the nanoparticles are maintained in a colloidal form in a solvent (e.g., in a water-based solvent) to which the dye can be added.
  • the Raman-active dye will provide the molecular vibrational energy levels needed to mediate the SECARS process.
  • the nanoparticles are suspended in a photopolymerizable resin.
  • photopolymerizable resin is known in the art and generally refers to a resin in which polymerization can be initiated via exposure to radiation having one or more suitable wavelengths (the radiation initiating polymerization in the resin is herein referred to as the polymerizing radiation).
  • the resin is preferably selected-to have an appropriate linear absorption spectrum such that blue-shifted anti- Stokes photons generated via coherent Raman scattering of radiation incident on the dye molecules, as discussed in more detail below, would cause polymerization of the resin only around those nanoparticles that efficiently enhance the Raman scattering process, e.g., those nanoparticles that provide a Raman scattering enhancement factor greater than a threshold value. As noted above, these nanoparticles are herein referred to as SERS-active particles.
  • the resin surrounding the nanoparticles that do not provide a significant Raman scattering enhancement remains substantially (or in many cases entirely) unpolymerized, as the generation of blue-shifted anti-Stokes photons by the dye molecules surrounding such particles is not significantly enhanced by the nanoparticles.
  • suitable photopolymerizable resins include, without limitation, photoresists, photoinitiator-monomer mixtures, and other optically curable polymer mixtures.
  • step (3) coherent anti-Stokes Raman scattering (CARS) is employed to cause polymerization of the resin surrounding those nanoparticles that provide a large SERS enhancement factor, e.g., an enhancement factor greater than about 10 4 and preferably greater than about 10 7 .
  • CARS coherent anti-Stokes Raman scattering
  • various portions of the resin in which the nanoparticles are suspended can be illuminated with pump and Stokes radiation to cause generation of blue-shifted anti-Stokes photons via coherent Raman scattering by the adsorbed dye molecules.
  • the nanoparticles that exhibit large Raman scattering enhancement factors can lead to efficient generation of blue shifted anti-Stokes photons via their adsorbed dye molecules with sufficient intensity to cause polymerization of the resin surrounding those nanoparticles.
  • the blue-shifted anti-Stokes photons are not efficiently generated (if generated at all) via the dye molecules adsorbed on the nanoparticles that do not provide significant Raman scattering enhancement factors (as noted above, these nanoparticles are herein referred to as SERS-inactive nanoparticles).
  • SERS-inactive nanoparticles As a result, the resin surrounding such SERS-inactive nanoparticles remains substantially (or entirely) unpolymerized.
  • CARS is a non-linear four-wave mixing process in which two pump photons and one Stokes photon are mixed to yield a blue-shifted anti-Stoke photon.
  • This process is mediated by a resonant vibrational energy state of a molecule (in this embodiment the energy state of the dye molecule).
  • the CARS anti-Stokes emission is coherent.
  • the intensity of the coherent output can be enhanced by several orders of magnitude when the difference of the pump and Stokes photon energies equals a vibrational energy of a molecule.
  • FIGURE 2 presents a schematic energy diagram depicting spontaneous Raman scattering and CARS four-wave mixing processes.
  • the pump photons (arrows Pl and P2) and Stokes photons (arrow S) are tuned to have an energy difference equal to a vibrational energy state of the molecule (the dashed lines represent virtual states, while the solid lines represent real vibrational states).
  • the input pump and Stokes photons cause the generation of blue shifted anti-Stokes photons (AS arrow).
  • the incident pump laser frequency can be selected to coincide with a fundamental surface plasmon resonance of the nanoparticles in solution.
  • the Stokes laser frequency is preferably selected to be CARS-resonant with a large wavenumber vibrational frequency of the molecule (in this implementation the dye molecule ) adsorbed onto the nanoparticles. Further, in many embodiments, the Stokes laser frequency is preferably selected to be non-resonant with a large number (and preferably all) of the vibrational frequencies of the solution or the resin.
  • the resin is preferably selected such that the pump and Stokes laser frequencies lie outside of its linear absorption spectrum.
  • the Raman-active molecules adsorbed onto the nanoparticles are preferably chosen in many embodiments to exhibit a strong, large wavenumber Raman band such that the anti-Stokes photons would spectrally lie within the linear absorption band of the resin. The choice of a high wavenumber Raman band can ensure that the pump and the Stokes photons would not cause direct polymerization of the resin.
  • the SERS-active and SERS- inactive nanoparticles can be separated based on the additional polymeric mass added to the SERS-active nanoparticles due to the polymerization of their surrounding resin.
  • separation can be achieved using centrifugation.
  • Other techniques based on the difference in size or mobility of nanoparticles having the added polymeric mass relative to the other nanoparticles can also be employed.
  • the polymerized resin and the adsorbed Raman-active molecules are removed from the separated SERS-active nanoparticle, e.g., by chemical washing or plasma treatment.
  • the nanoparticles can then be re-suspended in a desired solvent, yielding a solution of SERS-active nanoparticles.
  • the above process can be implemented without using the dye molecules to mediate the generation of the anti-Stokes radiation.
  • localized SERS enhancement provided by some of a plurality of particles suspended in a Raman-active photopolymerizable resin can be used to generate CARS anti-Stokes photons via resin molecules in close vicinity of those particles (e.g., on the surface of the particles) but not in the bulk of the resin far away from those particles.
  • a plurality of particles can be suspended in a photopolymerizable resin and the resin can be illuminated such that the resin molecules on the surface of the particles exhibiting a high SERS enhancement factor (e.g., an enhancement factor greater than about 10 4 or greater than about 10 6 ) would mediate the generation of anti-Stokes photons.
  • a high SERS enhancement factor e.g., an enhancement factor greater than about 10 4 or greater than about 10 6
  • These photons can in turn cause selective polymerization of the resin surrounding those particles that provide high SERS enhancement, thereby selectively adding polymeric mass to those particles.
  • a variety of parameters can be varied in the above process to adjust the criteria for selecting SERS-active nanoparticles. For example, by lowering the concentration of the dye in the nanoparticle incubation step such that there is an average of one molecule adsorbed on each nanoparticle, only those nanoparticles that provide sufficient Raman scattering enhancement to yield single-molecule SECARS would be selected (the resin surrounding only those particles would be polymerized, thus leading to their selection). Further, tuning the intensity of the pump and Stokes laser pulses will enable control over the magnitude of the Raman enhancement required to polymerize the resin.
  • a high average power table-top picosecond laser system can be employed to subject a large volume (e.g., about 1 milliliter) of a nanoparticle- resin solution to the SECARS process using a single laser pulse.
  • a large volume e.g., about 1 milliliter
  • the above nanoparticle separation process can be performed at a very high throughput rate, e.g., on the order of one liter per second (not including centrifuge and resin removal time).
  • FIGURE 3 schematically depicts an example of such a laser system 10 that includes a Ti:sapphire oscillator 12 that functions as a mode-locked laser to produce picosecond optical pulses at a wavelength of 800 nm.
  • the pulses can be amplified by a Ti: sapphire regenerative amplifier 14, which can operate based on chirped pulse amplification (CPA).
  • the amplified pulses are then split by a 50:50 beamsplitter (BS) 16 in order to concurrently pump two optical parametric amplifiers (OPAl , OP A2).
  • BS beamsplitter
  • these optical parametric amplifiers provide two picosecond pulses with an energy of approximately 50 microJoules over a tunable wavelength range of about 350 nm to about 1800 nm.
  • the wavelengths are chosen to be near (but not within) the optical absorption band of the photopolymerizable resin, as well as near the surface plasmon resonance frequency of the nanoparticles.
  • the two optical parametric amplifiers can be tuned to be separated in wavelength by an amount corresponding to a vibrational energy level of the Raman-active molecule (e.g., a dye molecule in this embodiment) adsorbed onto the nanoparticles.
  • the pulses generated by the OPAl are reflected by a mirror 20 to be recombined with the pulses generated by the OP A2 via a beamsplitter 22 into a single radiation beam that can be directed via mirrors 24 and 26 onto a sample under investigation.
  • the optical system 10 is provided for illustrative purposes and other systems can be also be employed to practice the separation methods of the invention.
  • the nanoparticles can be formed of aggregates of gold or silver atoms, with the fundamental surface plasmon resonances of the nanoparticles lying in the violet to green region of the visible spectrum.
  • the pump and the Stokes laser radiation can be provided by two optical parametric amplifiers pumped by a picosecond titanium: sapphire regenerative amplifier, such as those discussed above in connection with the system shown in FIGURE 3.
  • the amplifier can be seeded by a tunable titanium-sapphire picosecond amplifier.
  • Such a system can provide independently-tunable, picosecond pump and Stokes wavelength pulses at a repetition rate of about 1 kHz.
  • the system can provide pulse energies in the range of about 150 microJoules across the wavelength range of about 350 nm to about 1100 nm.
  • Such wavelength flexibility can allow matching the pump wavelengths to the plasmon resonances of both gold and silver nanoparticles, as well as eliciting SECARS signals from different vibrational modes of molecules adsorbed to the nanoparticles.
  • the invention provides methods for separating carbon nanotubes based on their semiconducting or metallic character (e.g., based on their electrical conductivity).
  • Carbon nanotubes are known in the art as members of the fullerene structural family. Carbon nanotubes are allotropes of carbon with a nanostructure that can exhibit in many cases a length-to-diameter ratio greater than about 1,000,000. They are typically in the form of cylindrical structures with diameters of the order of a few nanometers.
  • a variety of carbon nanotubes, such as single-walled and multi-walled carbon nanotube are known.
  • both metallic and semiconducting nanotubes are known. Such nanotubes are typically grown in batches that contain both semiconducting and metallic nanotubes.
  • the use of carbon nanotubes in electronic devices requires that the nanotubes be of the correct type (semiconducting or metallic).
  • one exemplary method for separating semiconductor carbon nanotubes from metallic carbon nanotubes includes dispersing a plurality of carbon nanotubes, which can contain both semiconducting and metallic nanotubes, in a photopolymerizable medium (step 1).
  • the photopolymerizable medium has preferably a different Raman spectrum from that of either type of carbon nanotubes.
  • the Raman spectra of the medium and those of the two types of carbon nanotubes can be distinct.
  • the Raman spectrum of the medium and that of at least one type of the carbon nanotubes may have some overlap but exhibit sufficiently different Raman scattering cross-sections for at least one excitation wavelength to allow performing the methods of the invention, as discussed further below.
  • the dispersed mixture of the carbon nanotubes can be exposed to high intensity laser pulses of appropriately chosen wavelengths so as to generate anti-Stokes photons, via Raman scattering of the incident photons by the carbon nanotubes, which are blue-shifted from the incident photons (as noted above, this process is known as coherent anti-Stokes Raman scattering (CARS)).
  • the incident photons can include photons from two pump beams each at a wavelength of 425 nanometers ( ⁇ p ) and a Stokes beam at a wavelength of 454 nanometers ( ⁇ s ). The generation of the blue-shifted anti-Stokes photons is enhanced when the pump and the
  • the intensity of the CARS blue- shifted anti-Stokes photons generated by an individual nanotube will be determined by whether or not the incident photons are in resonance with a vibrational frequency of that nanotube.
  • the wavelengths of the incident photons can be selected (e.g., 425 nanometers corresponding to ⁇ p and 454 nanometers corresponding to X 5 ) such that the incident radiation is in resonance with one type of nanotubes and not with the other.
  • the intensity of the blue-shifted photons generated by the nanotubes in resonance can be significantly greater than the respective intensity of such photons (if any) generated by the nanotubes that are not in resonance with the incident radiation.
  • the photopolymerizable medium (resin) in which the nanotubes are dispersed is chosen such that it would absorb the generated blue-shifted anti-Stokes photons and undergo polymerization when exposed to those photons. More specifically, the resin is selected such that the blue-shifted photons generated via the nanotubes scattering on resonance will be absorbed by the surrounding polymerizable medium to cause polymerization, thereby adding polymer mass to those nanotubes that are on resonance with the incident radiation.
  • photopolymerizable medium surrounding the nanotubes that are not on resonance with the incident radiation remains substantially (or entirely) unpolymerized, as these nanotubes do not generate blue-shifted anti-Stokes photons with sufficient intensity, even if they generate them, so as to cause significant polymerization of the photopolymerizable medium surrounding them.
  • polymeric mass is selectively added to one type of the nanotubes, but not the other (even if some polymeric mass is added to the carbon nanotubes that are off-resonance, the mass selectively added to the on-resonance carbon nanotubes is significantly greater that the mass added to the off-resonance nanotubes). In other words, mass is added selectively to the carbon nanotubes based on whether they are metallic or semiconducting.
  • the nanotubes can be separated, e.g., via centrifugation, based on their mass differences. More specifically, the nanotubes on resonance with the incident photons are removed from the rest, thus separating metallic and semiconducting nanotubes. Techniques other than centrifugation can also be employed. For example, the mass selectively added to the on-resonance carbon nanotubes can change their mobility and/or size relative to off-resonance nanotubes, allowing their separation.
  • the polymeric mass attached to the separated nanotubes that were on resonance with the incident radiation can be removed by employing techniques known in the art, such as chemical washing, or plasma treatment. Once semiconducting and metallic nanotubes are separated, they can be selectively used in a variety of applications, including molecular electronic devices.
  • this above separation process can be scaled up to separate large quantities of nanotubes in a short period of time.
  • the invention provides methods of selectively isolating one or more nanoparticles (e.g., carbon nanotubes), or selectively removing one or more carbon nanotubes, that are deposited over a substrate.
  • nanoparticles e.g., carbon nanotubes
  • These methods generally rely on generation of blue-shifted anti-Stokes photons to selectively expose portions of a photoresist layer covering the nanoparticles to those photons. Such exposure can cause a change in the exposed portions (e.g., polymerize those portions or increase their solubility to a developing agent), which can in turn be employed to achieve isolation of the nanoparticles or their selective removal, as discussed in more detail below.
  • the salient features of the methods are discussed in connection with carbon nanotubes. These methods can also be applied to other types of nanoparticles exhibiting suitable characteristics, e.g., appropriate Raman-active vibrational modes and/or suitable electronic states resonance(s).
  • a photoresist layer 34 can be formed over the substrate so as to cover at least a portion of the carbon nanotubes (step 1).
  • the thickness of the photoresist layer can be, e.g., a few microns.
  • the photoresist layer can be spin-cast over the carbon nanotubes to form a thin layer with a thickness, e.g., in a range of about 0.1 microns to about 5 microns.
  • the photoresist is preferably chosen so as to be transparent, or at least substantially transparent, to radiation applied in a subsequent step to cause generation of anti-Stokes photons via coherent Raman scattering of incident radiation by some of the carbon nanotubes, as discussed below. Further, the photoresist is preferably chosen such that at least one Raman active mode of the carbon nanotubes would be distinct from the Raman active modes of the photoresist. In some cases, the Raman spectrum of the photoresist and that of the carbon nanotubes may have some overlap but exhibit sufficiently different Raman scattering cross-sections for at least one excitation wavelength to allow performing the subsequent steps.
  • the photoresist is a negative -tone photoresist that can undergo polymerization, which renders it insoluble to a developing agent, in response to exposure to radiation having a suitable wavelength that would correspond to the wavelength of anti-Stokes photons generated via resonant Raman scattering of incident photons by the carbon nanotubes, as discussed further below.
  • the photoresist is chosen so as to exhibit good electrical insulation upon undergoing polymerization.
  • suitable photoresists include, without limitation, resists marketed by MicroChem Corp. of Newton, Massachusetts, U.S.A. under trade designations SU-8.
  • the carbon nanotubes (or in some cases, Raman active molecules in their vicinity) can be exposed to incident radiation, e.g., by scanning high intensity laser pulses over the sample, so as to generate blue shifted coherent anti-Stokes photons via resonant Raman scattering of the incident photons by the nanotubes (e.g., via CARS process), or in some cases by a Raman-active compound in the vicinity of the nanotubes (e.g., via SECARS process) (step 2).
  • incident radiation e.g., by scanning high intensity laser pulses over the sample, so as to generate blue shifted coherent anti-Stokes photons via resonant Raman scattering of the incident photons by the nanotubes (e.g., via CARS process), or in some cases by a Raman-active compound in the vicinity of the nanotubes (e.g., via SECARS process) (step 2).
  • the incident photons can include photons from two pump beams and a Stokes beam such that the pump and the Stokes photons are separated in frequency by an amount equal to the vibrational frequency of a Raman-active mode of the carbon nanotubes.
  • the two pump beams can be each at a wavelength of 425 nanometers ( ⁇ p ) and a Stokes beam at a wavelength of 454 nm ( ⁇ s ).
  • the frequency of the pump photons or that of the Stokes photons corresponds to the frequency of at least one electronic states transition of the carbon nanotubes.
  • the anti-Stokes photon can be absorbed by the photoresist surrounding the carbon nanotubes.
  • a layer of the negative-tone photoresist surrounding the carbon nanotubes undergoes polymerization and as a result becomes insoluble to a developing agent, such as propylene glycol monomethyl ether acetate (PGMEA) and acetone, while the unexposed portions of the photoresist remain soluble to the developing agent.
  • PGMEA propylene glycol monomethyl ether acetate
  • the polymerized photoresist forms an electrically insulating coating 30a that surrounds the carbon nanotubes, thereby electrically isolating the nanotubes from electrical leads that can subsequently be deposited on top of the polymerized and unpolymerized nanotubes.
  • a developing agent can be applied to the photoresist layer to remove the unexposed portions of the photoresist, which are soluble to the agent while leaving the exposed portions of the photoresist (portions exposed to the anti- Stokes radiation at sufficient intensity to undergo polymerization) surrounding the carbon nanotubes substantially, and preferably entirely, intact.
  • the plurality of carbon nanotubes include different types where some of the nanotubes exhibit one or more Raman active modes in resonance with the frequency difference between the pump and the Stokes photons (resonant carbon nanotubes) while the others do not (non-resonant carbon nanotubes).
  • the resonant carbon nanotubes can be electrically isolated in a manner discussed above without affecting the non- resonant carbon nanotubes.
  • the electrically- insulating, non-conducting layer of the exposed photoresist surrounding the carbon nanotubes can provide electrical isolation between the nanotubes and other components of a circuit present on a substrate. Such electrical isolation can prevent short circuits in electrical circuitry that employs carbon nanotubes as circuit elements.
  • FIG. 7 shows parts of an electrical device 36 (e.g., a field effect transistor) that includes two electrical contacts 38 and 40 (e.g., metal pads) placed on portions of a plurality of carbon nanotubes 30 that extend between two electrical contacts to form electrical contact therewith.
  • an electrical device 36 e.g., a field effect transistor
  • FIGURE 8 schematically depicts a field effect transistor 41 formed on a silicon wafer 42.
  • the transistor 41 includes a back gate contact layer 44, and two electrical contacts 46 and 47 and carbon nanotube 49 that is electrically insulated along at least an axial portion thereof via an insulating layer 49a (e.g., polymerized layer) by utilizing the above teachings.
  • the carbon nanotube 49 is electrically insulated from the contacts 46 and 47 by its insulating coating.
  • the contacts 46 and 47 function as source and drain contacts while the carbon nanotube 49 functions as the channel of the device.
  • a top-gate rather than a back-gate, can be utilized, where a gate contact can be placed on tope of an electrically insulating layer covering the nanotube (but the source and the drain contacts remain electrically contacted to the nanotube).
  • the gate voltage causes an electric field to pull or push charge carriers onto or off of the nanotube from the substrate, thereby altering the nanotube's electrical conductivity.
  • the invention provides methods for selectively removing one type of carbon nanotubes (e.g., metallic nanotubes) from a collection of nanotubes of different types disposed over a substrate.
  • resona ⁇ t nanotube refers to a nanotube that includes at least one Raman active mode that can resonantly scatter photons, for given pump and Stokes frequencies, in a CARS process to coherently generate anti-Stokes photons and/or includes an electronic states transition, or a plasmon resonance, at a frequency corresponding to that of the pump photons and/or the Stokes photons.
  • non-resonant nanotube refers to a nanotube that does not include such a Raman active vibrational mode at the difference frequency between the pump and Stokes frequencies, and nor does it include an electronic states transition (or a plasmon resonance) at a frequency corresponding to the frequency of the pump photons or that of the Stokes photons.
  • the resonant nanotubes can mediate generation of anti-Stokes photons (e.g., via a CARS or SECARS process)
  • the non-resonant nanotubes are not capable of mediating the generation of a substantial amount of anti-Stokes photons, if any.
  • a layer of a positive-tone photoresist 51 is a layer of a positive-tone photoresist 51
  • nanotubes 53a and 53b of different types can be formed over a collection of nanotubes 53a and 53b of different types disposed over an underlying substrate (e.g., a silicon wafer) 57 to contain the nanotubes (step 1).
  • the nanotubes 53a can be metallic (e.g., they can exhibit ohmic conductivity properties) while the nanotubes
  • the thickness of the photoresist layer can be, e.g., in a range of about 0.1 microns to about 5 microns.
  • the photoresist is preferably chosen to be transparent, or at least substantially transparent, to incident radiation applied in a subsequent step to generate anti-Stokes photons, as discussed below, and capable of absorbing anti-Stokes radiation via resonant Raman scattering of incident photons by at least some of the carbon nanotubes to enhance its solubility in a developing agent.
  • the nanotubes can then be exposed to incident radiation, e.g., by scanning pulsed radiation over the substrate surface, so as to produce anti-Stokes photons via resonant Raman scattering of the incident photons from the resonant nanotubes.
  • incident radiation e.g., by scanning pulsed radiation over the substrate surface
  • the generated anti-Stokes photons are absorbed by portions of the resist surrounding the resonant nanotubes.
  • the photoresist, the pump and Stokes beams, as well as the Raman active mode of the resonant carbon nanotubes are chosen such that the photoresist would absorb the anti-Stokes photons to enhance its solubility to a developing agent.
  • the photoresist surrounding the non-resonant nanotubes is not exposed to such anti-Stokes photons, or is exposed to only low levels of such anti-Stokes photons.
  • the incident photons can include two pump beams and a Stokes beam separated in frequency by an amount corresponding to a Raman active vibrational frequency of the resonant carbon nanotubes, but different (off- resonance) relative to the Raman active vibrational frequencies of the non-resonant carbon nanotubes.
  • the pump frequency or the Stokes frequency can be selected to be in resonance with an electronic states transition of the resonant carbon nanotubes.
  • anti-Stokes photons are generated via coherent Raman scattering of the incident photons by the resonant carbon nanotubes. At least a portion of the anti-Stokes photons are absorbed by a portion of the photoresist surrounding the resonant carbon nanotubes.
  • the photoresist is selected to be a positive-tone resist that would exhibit enhanced solubility to a developing agent in response to absorption of the anti-Stokes photons.
  • the photoresist surrounding the non-resonant carbon nanotubes remains insoluble to the developing agent as the non-resonant carbon nanotubes do not mediate significant generation of anti-Stokes photons.
  • FIGURE 1OB schematically shows that a portion of the photoresist (shaded portion) surrounding a resonant carbon nanotube 53b that has been exposed to anti-Stokes photons while the other portions, including those surrounding the non- resonant carbon nanotubes, have not been exposed to such anti-Stokes photons.
  • the portions of the photoresist that were exposed to the anti-Stokes photons surrounding the resonant carbon nanotubes can be removed, e.g., by dissolving the exposed portions of the photoresist in a developing agent in a manner known in the art of lithography to expose (uncover) the resonant carbon nanotubes, e.g., resonant carbon nanotube 53b shown schematically in FIGURE 1OC, while the non- resonant carbon nanotubes (e.g., carbon nanotubes 53a) remain covered by the photoresist.
  • a developing agent include, without limitation, aqueous alkaline developers.
  • the uncovered resonant carbon nanotubes can be removed from the substrate, e.g., via chemical or physical etching processes (acid, plasma, etc), leaving behind on the substrate the covered, non-resonant carbon nanotubes (step 4), as shown schematically in FIGURE 1OD.
  • the unexposed photoresist can then be optionally removed, e.g., by employing a chemical treatment (typically known in the art as a "stripping" process). In this manner, the selective removal of the resonant carbon nanotubes from the substrate can be achieved. In other cases, a negative photoresist can be employed to selectively remove non- resonant carbon nanotubes from a collection of resonant and non-resonant carbon nanotubes disposed over a substrate.
  • the anti-Stokes photons generated by coherent Raman scattering of incident radiation by the resonant carbon nanotubes can cause polymerization of a portion of the photoresist surrounding the resonant nanotubes to render those portions insoluble to a developer, while the unexposed portions remain soluble to the developer. The soluble portions can then be removed to uncover the non-resonant nanotubes and remove them.

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Abstract

L’invention concerne, sous un aspect, des procédés et des systèmes pour séparer des particules qui présentent des caractéristiques Raman différentes. Par exemple, un tel procédé peut comprendre l’introduction d’une pluralité de nanoparticules, sur chacune desquelles une ou plusieurs molécules actives Raman sont adsorbées, dans une résine pouvant être photopolymérisée et l’exposition des nanoparticules à un rayonnement de façon à exciter au moins un mode de vibration actif Raman des molécules afin de générer un rayonnement décalé Raman ayant une longueur d'onde appropriée pour polymériser la résine de telle sorte que le rayonnement décalé Raman entraîne une polymérisation sélective d’au moins une partie de la résine entourant une nanoparticule si la nanoparticule fournit un facteur d’amplification Raman supérieure à un seuil. Sous d’autres aspects, des procédés pour isoler électriquement une ou plusieurs nanoparticules ou pour enlever sélectivement un type de nanoparticules d’un ensemble de nanoparticules de types différents, disposées sur un substrat, sont divulgués. Ces procédés reposent de façon générale sur la génération de photons anti-stokes décalés vers le bleu pour exposer sélectivement des parties d’une couche de résine photosensible couvrant les nanoparticules de ces photons. A titre d'exemple, une telle exposition peut entraîner un changement des parties exposées (par exemple polymériser ces parties ou augmenter leur solubilité dans un agent révélateur), ce qui peut être employé pour obtenir un isolement des nanoparticules ou leur élimination sélective.
PCT/US2009/044848 2008-05-21 2009-05-21 Séparation de nanoparticules utilisant une diffusion raman anti-stokes cohérente WO2009143351A2 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012106608A1 (fr) * 2011-02-05 2012-08-09 Temple University - Of The Commonwealth System Of Higher Education Détection raman stimulée à l'aide de filament

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8968586B2 (en) * 2012-02-15 2015-03-03 Jsr Corporation Pattern-forming method
WO2017123325A1 (fr) * 2016-01-13 2017-07-20 William Fitzhugh Procédés et systèmes pour séparer des nanotubes de carbone
CN107127333B (zh) * 2017-05-22 2019-04-02 哈尔滨工业大学 一种通过振荡和沉降提纯银纳米线的方法
CN108931515B (zh) 2017-05-25 2023-09-15 三星电子株式会社 感测用基底和制造感测用基底的方法
US11251374B2 (en) * 2019-10-10 2022-02-15 Government Of The United States Of America, As Represented By The Secretary Of Commerce Nanotube spectrometer array and making a nanotube spectrometer array

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040038251A1 (en) * 2002-03-04 2004-02-26 Smalley Richard E. Single-wall carbon nanotubes of precisely defined type and use thereof
US20040191920A1 (en) * 2003-02-21 2004-09-30 Stuart Farquharson Simultaneous chemical separation and plural-point surface-enhanced raman spectral detection
US20060191374A1 (en) * 2000-05-26 2006-08-31 Guillet James E Cross-linked polymeric nanoparticles and metal nanoparticles derived therefrom
US20070258880A1 (en) * 2004-02-16 2007-11-08 Japan Science And Technology Agency Carbon Nanotube Structure-Selective Separation and Surface Fixation

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6610351B2 (en) * 2000-04-12 2003-08-26 Quantag Systems, Inc. Raman-active taggants and their recognition
JP3975266B2 (ja) * 2002-05-24 2007-09-12 独立行政法人産業技術総合研究所 細胞培養装置
US20040142484A1 (en) * 2002-09-30 2004-07-22 Intel Corporation Spectroscopic analysis system and method
JP4619130B2 (ja) * 2002-11-27 2011-01-26 ウィリアム・マーシュ・ライス・ユニバーシティ 官能基化カーボンナノチューブポリマー複合体および放射線との相互作用
US7247670B2 (en) * 2004-08-24 2007-07-24 General Electric Company Nanotubes and methods of dispersing and separating nanotubes
US7481990B2 (en) * 2005-01-27 2009-01-27 The Research Foundation Of State University Of New York Methods for osmylating and ruthenylating single-walled carbon nanotubes
US7923075B2 (en) * 2006-07-17 2011-04-12 The Hong Kong University Of Science And Technology Methods for preparing nanotextured surfaces and applications thereof
WO2008091852A2 (fr) * 2007-01-23 2008-07-31 President & Fellows Of Harvard College Substrats polymères pour spectroscopie raman
WO2011044221A2 (fr) * 2009-10-06 2011-04-14 Massachusetts Institute Of Technology Procédé et appareil pour déterminer un rayonnement
US8221592B2 (en) * 2009-11-18 2012-07-17 Korea University Research And Business Foundation Method for sorting carbon nanotubes (CNTs) and device for CNTs sorting
WO2012060827A1 (fr) * 2010-11-03 2012-05-10 Empire Technology Development Llc Lithographie utilisant un enduit photorésistant avec photoinitiateur et photoinhibiteur

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060191374A1 (en) * 2000-05-26 2006-08-31 Guillet James E Cross-linked polymeric nanoparticles and metal nanoparticles derived therefrom
US20040038251A1 (en) * 2002-03-04 2004-02-26 Smalley Richard E. Single-wall carbon nanotubes of precisely defined type and use thereof
US20040191920A1 (en) * 2003-02-21 2004-09-30 Stuart Farquharson Simultaneous chemical separation and plural-point surface-enhanced raman spectral detection
US20070258880A1 (en) * 2004-02-16 2007-11-08 Japan Science And Technology Agency Carbon Nanotube Structure-Selective Separation and Surface Fixation

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012106608A1 (fr) * 2011-02-05 2012-08-09 Temple University - Of The Commonwealth System Of Higher Education Détection raman stimulée à l'aide de filament
US9001325B2 (en) 2011-02-05 2015-04-07 Temple University —Of The Commonwealth System of Higher Education Filament-based stimulated Raman detection

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